Machine-tool for high speed machining adopting an ergonomic arrangement for functional parts thereof

ABSTRACT

A high speed machining machine-tool including a mechanical module having a machining station and a driving station and an equipment module with “n” number different parts located up line. The module bases are connected to a common supporting frame, with the mechanical module being fixedly connected thereto. The equipment module is connected to the machine so as to slide on its longitudinal axis. The different mobile parts of the machine-tool adopt two positions: a first, so-called “folded” position, in which the equipment module and all its parts engage each other and the mechanical module; a second, so-called “extended” position, in which the whole equipment module or a subset of its component parts have slid on the supporting frame towards the rear so as to form a transversal handling passage running through and through the machine. The invention is useful for high speed machining.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority under 35 U.S.C. § 119 toPatent Cooperation Treaty Application No. PCT/FR97/00976, filed on Jun.3, 1997, the entire contents of which are incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to machine-tools and more particularly, tothe arrangement of functional parts of a machine-tool for high speedmachining to ensure handling and maintenance under the best conditions.

2. Discussion of Background

High speed machining generally takes place using a tool rotatably drivenby the motor driven axis of an electric spindle installed in a ram,wherein the ram is mounted to be movable along X-, Y-, and Z-axes, whichare mutually perpendicular to each other.

A machine-tool is typically provided with four main working stations,which are:

(1) an actual machining station, including the machine-tool, drivenrotationally by the motor driven axis of the electric spindle, whereinthe machine-tool shapes the workpiece to be machined;

(2) a driving station situated up-line (or upstream) from the machiningstation, wherein the driving station is made up of a group of devicesthat ensure, in particular, X-, Y-, and Z-axes movements of the ram ofthe electric spindle, as well as feeding of the electric spindle for therotation of the electric spindle's tool carrier axis;

(3) a control station operating together with the driving station,wherein the control station functions by using a program ofpre-established instructions to take charge of the different stages ofmachining of the workpiece; and

(4) a magazine for storing tools in order to keep the machine-tools, tobe used in the machining process, near the machining area, during thedifferent stages of machining of the workpiece.

The machining station includes the machine-tool and electric spindle formachining the workpiece, wherein the machine-tool is driven by the motordriven axis of the electric spindle, which is fed by electric cablescoming from the control station. The electric spindle is housed in aram, which is movable in the X-, Y-, and Z-axes directions.

The driving station includes all of the motor elements to ensure the X-,Y-, and Z-axes movements of the ram.

The control station is connected to an electric group and a hydraulicgroup, as necessary, in order to distribute electric and hydraulicpower, respectively, and to ensure control of the components using theelectric and hydraulic power, respectively.

The function of the machine-tools is to machine the workpiece, in aminimum of time and with a maximum of precision. The shape of theworkpieces to be machined is becoming more and more complex, thusrequiring the use of several tools, from the nearby tool magazine, oreven several machine-tools to ensure complete machining of theworkpiece. A configuration including several of the machine-tools takingpart in the machining of the same workpiece is called a “machinetransfer.” A “machine transfer” can become a “flexible workshop” toensure the complete machining of several different workpieces. A“machine transfer” is a group of machine-tools which are placedperpendicular to the production line of the workpiece to achieve all themachining stages of that workpiece. Such an installation takes placewith respect to limiting factors, namely, the dimension of themachine-tools and especially, the floorspace available for themachine-tools. It is therefore essential, for reasons of cost and spacetaken up, that the machine-tools be compact in order to enable theinstallation of a “flexible workshop” or a “machine transfer.” In fact,a principal disadvantage of conventional machine-tools is that they takeup a very large amount of floorspace, despite the miniaturization of thecomponents that can presently be achieved. The size of the machine-toolcorresponds, first of all, to the machining to be done. In other words,to have a machine-tool that can be flexible, it has to adapt to allmachining types and to all dimensions. In any case, the electric spindleneeds to be of large dimensions to ensure a high speed of rotation or alarge engine power to enable the use of machine-tools of largedimensions. This leads to important dimensions of the ram andconsequently, important dimensions of the motor elements to ensure theram's movements in X-, Y-, and Z-axes directions. In the field in whichthe present invention applies, the machine-tools are of very largedimensions, so that the users lacking sufficient floorspace to house amachine-tool, must undertake extensions to their premises. This puts aconsiderable strain on the cost of installing there machine-tools, inaddition to the actual cost of the machine-tools.

Another disadvantage of the machine-tools for high speed machining isthe fact that it is necessary to authorize access to all the functionalparts or components of the machine-tool to ensure adequate maintenancethereof. As a result, access areas which permit an operator to ensurethe maintenance of the vital part of the machine-tool, in particular,access areas of the driving station, must be provided around doors,hatches, or windows. The doors, hatches, or windows were conceived toauthorize maintenance of the machine-tool, but increase the floorspaceneeded to set up each machine-tool. In “machine transfers,” even morefloorspace is needed, so that not only the amount of floorspace neededto install the machine-tool is increased, but the number of conveyorsconveying the workpieces from one machine-tool to another is increasedas well.

Another disadvantage of the machine-tools for high speed machining isthat they require the presence of a cooling group. In fact, thefunctioning of the machine-tools raises the temperature of theworkpieces at the driving station to a level which would be detrimentalfor the lifespan of the workpieces, if subsidiary cooling was not setup. This rise in temperature could also lead to the dilatation of theparts of the driving station, which would have as a consequence thereof,a non-negligible loss of precision in the machining of workpieces. Thecooling groups are generally of large dimension and are difficult tointegrate into the machine-tools.

Starting with these considerations with respect to the originalconfiguration of a machine-tool, applicant has attempted to reduce thefloorspace requirement of the machine-tool, while making it easier toaccess the vital parts for handling, replacement, repair, etc. Theconfiguration of the machine-tools of the present invention rests on aflexible ergonomic arrangement of the functional parts thereof, whileavoiding the disadvantages described above with respect to conventionalmachine-tools.

SUMMARY OF THE INVENTION

According to the present invention, the machine-tool for high speedmachining includes a mechanical module made up of a machining station, adriving station, and an equipment module. The equipment module has avariable number “n” of different parts located up-line. The bases of themechanical and equipment modules are connected to a common or communalsupporting frame. The mechanical module is fixedly connected to thecommon supporting frame. A longitudinal axis of the machine-tool for theequipment module is slidingly connected to the common supporting frame.The machine-tool has different parts, which are mobile and which adopteither of two positions, as follows:

(1) a first or “folded” position, wherein the equipment module and allof its different parts are placed against one another and against themechanical module; and

(2) a second or “extended” position, wherein the entire equipmentmodule, or a subset of its component parts, have slid on the supportingframe, towards the rear of the machine-tool, so as to form a firsthandling passage, which runs transversely through the machine-tool.

The above-described flexible ergonomic arrangement has the advantage ofadding only the width of the first handling passage to the lengthnecessary for installing the machine-tool. The access areas to the vitalparts of the machine-tool are considerably increased by the creation ofthe handling passage through the machine-tool, between each of themechanical and equipment modules and between each different partconstituting the mechanical and equipment modules.

Another advantage of the flexible ergonomic arrangement of themachine-tool of the present invention is the creation of a handlingspace running transversely through the machine-tool, while permittingthe operator access to the core of the machine-tool. Thus, access forthe handling or the maintenance of the different parts, from the insideof the machine-tool, permits the sides of the machine-tool to be keptfree from any component needing intervention or handling.

Another advantage of the flexible ergonomic arrangement of themachine-tool of the present invention is that it is easier to reach themotor elements of the machine-tool from its core than from the side.Consequently, instead of opening onto the outside perimeter of themachine-tool, the access hatches can open into a handling passage,created for this purpose by the separation of the control station andthe driving station.

Another advantage of the presence of the handling passage is that amachine-tool can be placed with one side against a wall, while stayingentirely functional and accessible for its maintenance. In addition, theclosing and the opening of the handling passage permits the placement ofthe machine-tool so as to be positioned in such a way that, its rearpart is against a corner of the wall. Thus, the closing of the handlingpassage into its “folded” position permits access to the rear of themachine-tool and, the opening of the handling passage between bothmechanical and equipment modules, or between the parts of the equipmentmodule, permits access to the internal components.

The “folded” position has the advantage of creating a compactmachine-tool. The closing of the handling passage ensures the protectionof the mechanical, electrical, and hydraulic vital parts from theoutside environment.

According to a particularly advantageous characteristic of the presentinvention, the machine-tool for high speed machining has a supportingframe, on which the equipment module slides. The supporting frame has alength such that when the equipment module does slide towards the rearof the machine-tool, either partially or as entirely, to arrive at theend of its course to go from a “folded” position to an “extended”position, a second handling passage is opened to permit handling betweenboth mechanical and equipment modules, so that when the equipment moduleslides, only partly in any direction, the second handling passagebetween the different parts is opened and the first handling passage,that was previously open, is closed.

According to another preferred embodiment of the present invention, themachine-tool for high speed machining includes a machining station, adriving station, a control station, and a control desk. The machining,driving, and-control stations are connected to a common supportingframe. The machining, driving, and control stations are fixed to thecommon supporting frame so that the machining station and the drivingstation are situated up-line from the common supporting frame, and areseparated from the control station by a handling passage runningtransversely through the machine-tool to permit access for an operator.

Two to three machine-tools can be placed in contact with one another.The machine-tools must have parallel Z-axes to ensure a savings of spacedue to the suppression of the intended gap between the machine-tools.This gap was previously necessary in order to enable an operator accessfrom the side for maintenance. Furthermore, when two or threemachine-tools are placed laterally against one another, the first andsecond handling passages, which are now fixed, pass through the alignedmachine-tools to ensure communication between the first and secondhandling passages from one machine to another.

According to another particularly advantageous characteristic of thepresent invention, the mechanical and equipment modules of themachine-tool for high speed machining adopt a significantlyparallelepipedic shape of the same width, thus ensuring a perfectsymmetry about the Z-axis. The symmetry of the machine-tool as a wholepermits several machine-tools to be place side by side in order toensure a compact configuration to save on the necessary space. Thissavings of space is at the level of the clearance areas and permits theintegration of more machine-tools onto the same floor area, when themachining line already includes a large number of machines. In addition,during the building and studying of the machine-tool installation onsite, the symmetry considerably simplifies the process in abolishing theconstraints of clearance areas and in setting up the accessories, suchas the tool magazine or the control desk, which can be placed either onthe right side or the left side of the machine-tool, depending on theway it was set up.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The fundamental concepts of the present invention having been exposedhereinabove in their most elementary form, more details andcharacteristics will come out more clearly when reading the descriptionhereinafter, using as a non-limitative example and having regard to theattached drawings, an embodiment of a machine-tool for high speedmachining with a flexible ergonomic arrangement of the functional partsaccording to the present invention. This description refers to theenclosed drawing figures, as follow.

FIG. 1 is a perspective view of a machine-tool adopting the presentinvention's flexible ergonomic arrangement of the functional parts.

FIG. 2 is a top view of a machine-tool adopting a fixed position of thehandling passage and the control station.

FIG. 3 is a top view of a “machine transfer”, including severalmachine-tools, to ensure the machining of a workpiece, and illustratesthe possibilities of the configuration offered by the flexible ergonomicarrangement of the functional pars of the machine-tools for high speedmachining of FIG. 2.

FIGS. 4a, 4 b, and 4 c are top views of the machine-tool of FIG. 1adopting several configurations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, the machine-tool M for high speed machining includesa mechanical module and an equipment module. The mechanical moduleincludes a machining station P2, a driving station P1, and a storagestation P4. The driving station P1 includes all of the motor elements.The storage station P4 includes a tool magazine which permits keepingall of the tools necessary for the different machining stages that themachine-tool M has to execute available in a sealed chamber. Theequipment module includes a control station P3 which includes severalcupboards and power groups.

According to the main characteristic of the present invention, themechanical and equipment modules are connected to a common supportingframe 700 on a base. The mechanical module is fixedly connected to thecommon supporting frame 700 and the equipment module is slidinglyconnected to the longitudinal axis of the machine-tool M.

As shown in FIG. 4a, the machine-tool M for high speed machining has anequipment module which is formed of two different parts. A first of thetwo different parts is a hydraulic group 600, which is placed againstthe mechanical module, when the machine-tool M is in its “folded”position, as illustrated. A second of the two different parts is asubset including a cooling group 300 and an electric cupboard 200. Thecooling group 300 and the electric cupboard 200 are situated at the rearof the machine-tool M so that movement therein creates first and secondhandling passages 100 and 100′, respectively.

The first handling passage 100 is opened between the mechanical module,formed by the machining station P2 and the driving station P1, and thehydraulic group 600, as shown in FIG. 4b. Thus, access to the hatch 500of the driving station P1 is permitted, as well as to the control partsof the hydraulic group 600, which are situated on the side of theelectric cupboard 200 of the hydraulic group 600.

The second handling passage 100′ is opened by the movement of theelectric cupboard 200 of the hydraulic group 600 towards the drivingstation P1 up to the position in full lock of the electric cupboard 200.Thus, the first handling passage 100, between the hydraulic group 600and the subset (i.e., the cooling group 300 and the electric cupboard200) is closed, as shown in FIG. 4c. The second handling passage 100′permits access to the hydraulic control parts situated on the side ofthe hydraulic group 600 and to the electric parts situated in theelectric cupboard 200, when the access doors 210 and 220 are opened.

According to a preferred embodiment of the present invention, theelectric cupboard 200, formed by the hydraulic group 600, does not havea transverse wall when in the “folded” position. The walls of thedriving station P1, on the one hand, and the walls of the electriccupboard 200, on the other hand, seal the parallelepiped formed by theelectric cupboard 200 of the hydraulic group 600.

According to a preferred embodiment of the present invention, theequipment module is formed by the subset (i.e., the electric cupboard200 and the cooling group 300) and the hydraulic group 600. Thehydraulic group 600 is slidingly mounted so as to translate onlongitudinal slides. When the machine-tool M goes from the “folded”position, as shown in FIG. 4a, to an “extended” position, as shown inFIGS. 4b or 4 c, the first and second handling passages 100 and 100′ arefitted with first and second duckboards 110 and 110, respectively. Thispermits an operator to have access from above, between the longitudinalslides.

According to a particularly judicious characteristic, the secondduckboard 110′ is fixed at the base of the hydraulic group 600. Thus,the second duckboard 110′ shows solidarity in all of its movements. Thesecond duckboard 110′ also fits under the electric cupboard 200, whenthe hydraulic group 600 is placed against the electric cupboard 200.Another advantage is that the hoses feeding the power are not disturbedby the presence of the second duckboard 110′, which is fixed, whencommunicating under the electric cupboards 200, between the differentparts of the equipment module, and between the mechanical and equipmentmodules.

According to another preferred embodiment of the present invention, thesubset (i.e., the cooling group 300 and the electric cupboard 200) has awidth equal to twice the width of the hydraulic group 600. The length,of the supporting frame 700 of the longitudinal slides, which permitsliding movement, is such that, when the machine-tool M is in its“folded” position, the total course of the equipment module or of onlythe subset, opens a handling passage having a width equal to the widthof the hydraulic group 600. Therefore, the width of the handling passageis equal to half the width of the subset. This characteristic isimportant in that, as shown in FIG. 1, it enables the machine-tool M toextend to a length longer than the length of the sliding of thesupporting frame 700. Thus, the subset is permitted an overhand of equalto half of its width. A shorter length of the frame 700 allows forfreedom from any obstacle or guidance part at the rear area of themachine-tool M. Thus, an optimal compactness of the machine-tool M inthe “folded” position is guaranteed.

As shown in FIG. 2, the machine-tool M for high speed machining,according to a second embodiment as illustrated, includes a machiningstation P2, a driving station P1, a control station P3, and a controldesk 400. The machining, driving and control stations P2, P1, and P3 areconnected to a common supporting frame 700. The machine-tool M for highspeed machining has different stations which are fixed to the commonsupporting frame 700. Thus, the machining station P2 and the drivingstation P1, which are situated up-line, are separated from the controlstation P3 by a first handling passage 100 running transversely throughthe machine-tool M to permit access for an operator. The control stationP3 includes an electric cupboard 200 to ensure the distribution and thecontrol of the electric parts of the machine-tool M and of a coolinggroup 300, which has its control on a side of the first handling passage100, to ensure a controlled temperature to the electric parts, which aresusceptible to a rise in temperature and to buckling.

According to a particularly advantageous characteristic of the presentinvention, the cooling group 300 is situated so as to open at the rearof the machine-tool M so that an operator can have access to thecontrols thereof. The advantage of this arrangement it that the coolinggroup 300 is left with an air gap opening to the outside, therebypermitting optimal ventilation. This advantage would not have beenpossible if the cooling group 300 had been situated between the electriccupboard 200 and the first handling passage 100. Furthermore, theelectric cupboard 200, which includes the electric components, issituated between the cooling group 300 and the first handling passage100. The access doors 210 and 220 of the electric cupboard 200 open intothe first handling passage 100. This particular arrangement has theadvantage of including all of the electric control components in thesame chamber. Since the chamber is accessible from the first handlingpassage 100, it does not need a door or access hatch on the side of themachine-tool M.

According to a particularly advantageous characteristic of the presentinvention, a control desk 400 of the machine-tool M is placed in thefirst handling passage 100 and is pivotally mounted on a bracket 410.The bracket 410 is mounted on a vertical axis of the frame 700 of themachine-tool M. In this way, the control desk 400 is either: in a turnedposition (as represented by broken lines) so that the first handlingpassage 100 is free for the operator; or is back inside of the firsthandling passage 100 (as represented by continuous lines) so as toprevent the entire machine-tool M from having any “wart-shaped”components on a side thereof.

According to another particularly advantageous characteristic of thepresent invention, the driving station P1 is fitted with an access hatch500, which opens into the first handling passage 100, thus permittingaccess to the vital parts of the machine-tool M (i.e., to the drivingmotor elements). This ensures the movement of the ram 800 in the X-, Y-,and Z-axes directions. The electric spindle 810 is housed in the ram 800to ensure the rotational driving of a tool or spindle 820.

According to a preferred embodiment of the present invention, thehydraulic plate used to distribute the hydraulic power is situated inthe driving station P1. Thus, the hydraulic plate is accessible from theaccess hatch 500 of the driving station P1.

The control desk 400 of the machine-tool M is housed, by rotation(continuous lines) of its bracket 410 on which it is fixed, inside ofthe first handling passage 100. It can therefore move apart to leavefree passage to an operator (broken lines). The electric cupboard 200and the cooling group 300 have a parallelepipedic shape which make theirdisposition easier in the compact group of the machine-tool M andpermits the machine-tool M to adopt a perfectly symmetricalconfiguration given that the tool magazine and the control desk 400 ofthe machine-tool M can change sides.

The “machine transfer”, as shown in FIG. 3, shows several machine-toolsM for high speed machining, placed in a machining line so as toparticipate in the machining of one or more workpieces. From theparticular arrangement of the functional parts, these machines can beplaced one against the other by two or three, while being completelyfunctional as to the maintenance of the vital parts, such as electriccomponents in the electric cupboard 200, are carried out from the rearof the machine-tool M and that the maintenance of the motor elements ofthe driving station P1 or of the parts of the cooling group 300, arecarried out in the core of the machine-tool M from the first handlingpassage 100. The groups of machine-tools M, placed one against another,are moved apart so as to permit access to the machining station P2 andto the tool magazine P4. The tool magazine P4 is advantageously placedon the side permitting access. The access to the tool magazine P4 and tothe machining station P2 of the machine-tool M situated between twoother tool-machines M is allowed when no machine-tools M are placedopposite to it. A “machine transfer” carried out with the machine-toolsM of the present invention takes a lot less space than with conventionalmachine-tools for high speed machining.

Another advantage of the machine-tools M having a flexible ergonomicarrangement of functional parts thereof and in “machine transfer” isthat the first handling passages 100 of each of the machine-tools M arein a line to form a large handling passage permitting the creation of acontinuous handling line.

It is understood that the machine-tool for high speed machining of thepresent invention adopts a flexible, ergonomic arrangement for itsfunctional parts which have been described and represented hereinabove.The functional parts are given for the purpose of disclosure and notlimitation. It is obvious that various arrangements of, as well asmodifications and improvements to, the above-described example will bepossible without departing from the scope of the present invention takenin its broadest aspects and spirit. For example, several technologicalsolutions could be adopted to ensure the movement of the functionalparts of the equipment module of the module as a whole on thelongitudinal axis of the machine-tool.

In order to permit better understanding of the drawings, a list of thereference symbols with their explanations is presented, as follows:

M machine-tool;

P1 driving station;

P2 machining station;

P3 control station;

P4 tool storage station;

100 first handling passage;

100′ second handling passage;

110 first duckboard;

110′ second duckboard;

200 electric cupboard;

210 access door (to electric cupboard 200);

220 access door (to electric cupboard 200);

300 cooling group;

400 control desk;

410 bracket;

500 access hatch (to driving station P1);

600 hydraulic group;

700 common supporting frame;

800 ram;

810 electric spindle; and

820 tool or spindle.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A machine-tool for high speed machining, saidmachine-tool comprising: a supporting frame; and a mechanical modulehaving a base fixedly connected to said supporting frame, saidmechanical module comprising, a machining station, a driving station;and an equipment module having both a plurality of different partslocated up-line and a base slidingly connected to said supporting framealong a longitudinal axis of said machine-tool, wherein said pluralityof different parts of the said equipment module can adopt any one of twopositions including a first position, wherein said equipment module andsaid plurality of different parts are placed both against one anotherand against said mechanical module, and wherein a second position,wherein when any one of an entirety of said equipment module and asubset of said plurality of different parts of said equipment modulehave slid on said supporting frame towards a rear of said machine-tool,a first handling passage is formed transversely through saidmachine-tool.
 2. The machine-tool according to claim 1, wherein a lengthof said supporting frame on which said equipment module slides is suchthat when said any one of said entirety of said equipment module andsaid subset of said plurality of different parts of said equipmentmodule slide towards said rear of said machine-tool and arrives at anend of a course thereof to go from said first position to said secondposition, said first handling passage is formed to permit handlingbetween said mechanical and equipment modules, such that when saidequipment module slides, only partly in any direction, a second handlingpassage is formed between said plurality of different parts of saidequipment module and said first handling passage, which was previouslyopen, becomes closed.
 3. The machine-tool according to claim 1, whereinsaid plurality of different parts of said equipment module includes ahydraulic group, which is placed against said mechanical module whensaid machine-tool is in said first position and said subset of saidequipment module, which includes a cooling group and an electriccupboard situated at said rear of said machine-tool so that movement ofsaid cooling group and said electric cupboard creates said firsthandling passage and a second handling passage, respectively, said firsthandling passage between said mechanical module and said hydraulic groupof said equipment module and said second handling passage between saidhydraulic group of said equipment module and said subset of saidequipment module including said cooling group and said electriccupboard.
 4. The machine-tool according to claim 1, further comprising amachining station, a driving station, a control station and a controldesk, wherein said machining, driving, and control stations areconnected to a communal supporting frame, and wherein said machining,driving, and control stations are fixed to said communal supportingframe so that said machining station and said driving station, which aresituated up-line from said communal supporting frame, are separated fromsaid control station by a passage running transversely through saidmachine-tool to permit access for an operator.
 5. The machine-toolaccording to claim 4, wherein said control station includes a coolinggroup, and wherein said cooling group is situated so as to open at saidrear of said machine-tool for the operator to have access to controlsthereof.
 6. The machine-tool according to claim 4, wherein said controlstation includes a cooling group and an electric cupboard, said electriccupboard including electric components, said electric cupboard beingsituated between said cooling group and said first handling passage, andsaid electric cupboard having access doors which open onto said firsthandling passage.
 7. The machine-tool according to claim 6, wherein saiddriving station includes an access hatch at a rear thereof, said accesshatch opening onto said first handling passage between said controlstation and said driving station.
 8. The machine-tool according to claim2, wherein said control desk is mounted on a bracket, said bracket beingpivotally mounted on said communal supporting frame of said machine-toolpermitting said control desk to any one of close said first handlingpassage, open said first handling passage, and close and open said firsthandling passage, by rotation of said bracket.
 9. The machine-toolaccording to claim 8, wherein said hydraulic plate, used to distributehydraulic power, is situated in said driving station so that saidhydraulic plate is accessible by said access hatch of said drivingstation.
 10. The machine-tool according to claim 9, wherein saidmechanical and equipment modules adopt a slightly parallelepipedic shapehaving a width which is the same as a width of said machine-tool, thusensuring a perfect symmetry about a Z-axis.